Thank you for your message.
There seems to be some issues with this transformation method. I recommend you to create the link yourself. If you want to display e.g. image which is stored in Media Selector form control try building this url:
<img src="domain/getfile/<%# Eval("MediaSelector") %>/filename.aspx">">
The filename can be anything, it really doesnt matter what is there, the important is the guid.